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Moving Forward After PRRS Infection

Located in southern Clay County, Roy Henry's farm is five miles from any other hog operations. It doesn't seem like the kind of location a disease might strike, but in December 2012, Henry's farm broke with porcine reproductive and respiratory syndrome, or PRRS virus.

A year later, after having depopulated and repopulated from the first outbreak, his three finishing barns tested positive for PRRS on Christmas Eve, indicating the virus had found its way to the farm once again. Although the wet, cold weather was perfect for the virus with, it's still a question as to how the infection happened, he says. "We went 20 years and avoided PRRS, and then got it twice in 13 months," he says.

KEY BIOSECURITY BARRIERS: Biosecurity has been paramount for 20 years on Henry's farm. The farm has numerous barriers to prevent contamination, including in supplies handling, employee training, and transportation. He went 20 years without being infected with PRRS, and got it twice in 13 months.

There are several ways the virus typically spreads. Any body fluid from an infected pig contains the virus, so blood, semen, milk, urine, or feces carried from place to place may spread infection. Aerosol spread by respired droplets containing virus can transmit the agent. "Fomites" carry infected materials from one place to another, and can be as simple as packaging on supplies or as complex as the movement, clothing, and footwear of workers.

Biosecurity barriers
Biosecurity has been paramount to Henry's hog farm for the last 20 years. The farm has numerous barriers to prevent contamination, including in supplies handling, employee training, and transportation. For example, cleaning, washing, disinfecting trailers with an ounce of Synergize mixed with a gallon of water, and letting them dry between loads are regular practices – which Henry says should be enough to inactivate PRRS virus.

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After his farm broke in 2012, Henry added a new barrier – a thermo-assisted decontamination and drying, or TADD barn. This system heats trailers inside the barn after being cleaned and disinfected. Hot air is blown into the barn through a recirculation room, fans placed on the walls push air downward, and fans blow air through the trailers. This heat and drying system may reach virus that didn't come into contact with disinfectant.

In the TADD barn, remote sensors placed on certain parts of trailers monitor temperature over a period of time. These sensors are plugged into a computer to display temperature history. This way, Henry knows the coolest point on any trailer was 150 degrees when the virus broke – more than enough to kill PRRS, he says. "We had good reason to believe, once it had been cleaned, washed, disinfected, and had gone through the TADD, the trailer was the cleanest it could have been," he says. "I want to believe that the TADD was not the point that failed. I hope I'm correct."

Moving forward
Henry plans to step up biosecurity even further in the hopes of preventing future issues with PRRS or PED, also known as porcine epidemic diarrhea, which has been in the U.S. since May. He isn't taking chances in TADDing and disinfecting, which can also prevent PED. He plans to continue TADDing trucks after they are initially disinfected, but will add another layer by re-disinfecting them after TADDing with a solution of an ounce of Synergize in a gallon of water before letting it sit for an hour.

PRRS is resilient and capable of traveling long distances and mutating. So, Henry says he may never know how this strain came to his farm. "It's complicated in the fact that we don't know how it's getting here. If we did, we should be able to prevent it," he says. "The vectors are becoming more elusive as we speak."